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https://issues.apache.org/jira/browse/BAHIR-183?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16800091#comment-16800091
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Lukasz Antoniak commented on BAHIR-183:
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[~yanlin-Lynn], I suspect that you can loose messages while running the current
code version. MQTT guarantees QoS 1 and 2 thanks to client persistence to local
file system. Current implementation of MQTT source with HDFS back-end leverages
memory persistence for in-flight messages. If Spark application terminates
abnormally after picking up message from the broker, but before writing it to
HDFS, data can be lost. Did you explore the _MqttClientPersistence_ option?
> Using HDFS for saving message for mqtt source
> ---------------------------------------------
>
> Key: BAHIR-183
> URL: https://issues.apache.org/jira/browse/BAHIR-183
> Project: Bahir
> Issue Type: Improvement
> Components: Spark Structured Streaming Connectors
> Affects Versions: Spark-2.2.0
> Reporter: Wang Yanlin
> Assignee: Wang Yanlin
> Priority: Major
> Fix For: Spark-2.4.0
>
>
> Currently in spark-sql-streaming-mqtt, the received mqtt message is saved in
> a local file by driver, this will have the risks of losing data for cluster
> mode when application master failover occurs. So saving in-coming mqtt
> messages using a director in checkpoint will solve this problem.
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